A longitudinal physical profile assessment of skeletal muscle manifestations in myotonic dystrophy

Objectives: To develop an assessment that describes the skeletal muscle man ifestations in myotonic dystrophy subjects and then use it to quantify the presentation of skeletal muscle disability and to show change over time. Design: A quantified skeletal muscle assessment was developed and applied t hree times over a two-year period at intervals around 12 months. Thirty-six subjects with myotonic dystrophy and 20 subjects without neuromuscular dis ability were evaluated. The assessment comprised manual muscle testing of f ive pairs of muscles, measuring neck flexor strength with a strain gauge, r espiratory function tests, power and lateral pinch grip strength, all tests of impairment, Assessment of the ability to move from sitting to standing and fasten buttons tested disability. Results: Results from subjects with myotonic dystrophy were compared to the normal data. The subjects with myotonic dystrophy were significantly weake r in proximal upper limb muscles, quadriceps, tibialis anterior muscles and neck flexor muscles as well as power and lateral pinch grips. There was al so significant reduction in forced expiratory volume at one second (FEV1) a nd forced vital capacity (FVC). Significant disability was seen in the myot onics in moving from sitting to standing and in fastening buttons, Over the two-year study period proximal upper limb and lower limb muscle strength, FVC and sit-to-stand ability declined significantly. Power grip declined bu t lateral pinch grip and FEV1 improved significantly. Button fastening abil ity improved significantly. Conclusion: The test developed was shown to be reliable and sensitive to th e change in skeletal muscle manifestations in subjects with myotonic dystro phy who were shown to be significantly weaker than normal subjects.